private static final class Listener {
    static final Listener TOMBSTONE = new Listener();
    @CheckForNull // null only for TOMBSTONE
    final Runnable task;
    @CheckForNull // null only for TOMBSTONE
    final Executor executor;

    // writes to next are made visible by subsequent CAS's on the listeners field
    @CheckForNull Listener next;

        value = other.value;
        throwable = other.throwable;
        // don't copy the mayInterruptIfRunning bit, for consistency with the server, to ensure that
        // interruptTask() is called if and only if the bit is true and because we cannot infer the
        // interrupt status from non AbstractFuture futures.
        state = other.state;

        notifyAndClearListeners();
        return;
      }